According to a recent theory, Archean-age gold-quartz
vein systems were formed over two billion years ago from
magmatic fluids that originated from molten granitelike
Line bodies deep beneath the surface of the Earth. This theory is
(5) contrary to the widely held view that the systems were
deposited from metamorphic fluids, that is, from fluids that
formed during the dehydration of wet sedimentary rocks.
The recently developed theory has considerable practical
importance. Most of the gold deposits discovered during
(10) the original gold rushes were exposed at the Earth's surface
and were found because they had shed trails of alluvial
gold that were easily traced by simple prospecting methods.
Although these same methods still lead to an occasional
discovery, most deposits not yet discovered have gone
(15) undetected because they are buried and have no surface
expression.
The challenge in exploration is therefore to unravel the
subsurface geology of an area and pinpoint the position of
buried minerals. Methods widely used today include\
(20) analysis of aerial images that yield a broad geological
overview; geophysical techniques that provide date on the
magnetic, electrical, and mineralogical properties of
the rocks being investigated; and sensitive chemical tests that
are able to detect the subtle chemical halos that often
(25) envelop mineralization. However, none of these high-
technology methods are of any value if the sites to which
they are applied have never mineralized, and to maximize
the chances of discovery the explorer must therefore pay
particular attention to selecting the ground formations most
(30) likely to be mineralized. Such ground selection relies to
varying degrees on conceptual models, which take into
account theoretical studies of relevant factors.
These models are constructed primarily from empirical
observations of known mineral deposits and from theories
(35) of ore-forming processes. The explorer uses the models to
identify those geological features that are critical to the
formation of the mineralization being modeled, and then
tries to select areas for exploration that exhibit as many of
the critical features as possible.
The theory mentioned in line 1 relates to the conceptual models discussed in the passage in which of the following ways?
(A) It may furnish a valid account of ore-forming processes, and, hence, can support conceptual models that have great practical significance.
(B) It suggests that certain geological formations, long believed to be mineralized, are in fact mineralized, thus confirming current conceptual models.
(C) It suggests that there may not be enough similarity across Archean-age gold-quartz vein systems to warrant the formulation of conceptual models.
(D) It corrects existing theories about the chemical halos of gold deposits, and thus provides a basis for correcting current conceptual models.
(E) It suggests that simple prospecting methods still have a higher success rate in the discovery of gold deposits than do more modern methods.
Q/a-a why not b
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archean -age gold
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Ankitaverma
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Hi, I think I might be able to help. 
After reading the passage through, let's first look at the question and what it is asking:
After reading the question, I know that I need to return to the first line to remind myself of this theory, and then look for what this theory has to do with conceptual models discussed later in the passage.
And what does that mean? Well, basicially, we are talking about gold and how it formed. We could make it more complicated, but really all we are talking about here is a new theory about how gold-quartz formed a long time ago. Let's leave it at that and move on.
So now we learn that this theory will have practical importance. It will help in locating golf that is not on the surface. But this is not exactly what we are looking for. We need to find the conceptual models that relate to this new theory. And it is not until later in the passage we find out more about the connection between theories and models:
Alright, let's turn to our answer choices:
I hope that I was able to help a little bit.
Happy studying!
After reading the passage through, let's first look at the question and what it is asking:
The theory mentioned in line 1 relates to the conceptual models discussed in the passage in which of the following ways?
After reading the question, I know that I need to return to the first line to remind myself of this theory, and then look for what this theory has to do with conceptual models discussed later in the passage.
According to a recent theory, Archean-age gold-quartz
vein systems were formed over two billion years ago from
magmatic fluids that originated from molten granitelike
Line bodies deep beneath the surface of the Earth.
And what does that mean? Well, basicially, we are talking about gold and how it formed. We could make it more complicated, but really all we are talking about here is a new theory about how gold-quartz formed a long time ago. Let's leave it at that and move on.
The recently developed theory has considerable practical
importance....most deposits not yet discovered have gone
(15) undetected because they are buried and have no surface
expression.
So now we learn that this theory will have practical importance. It will help in locating golf that is not on the surface. But this is not exactly what we are looking for. We need to find the conceptual models that relate to this new theory. And it is not until later in the passage we find out more about the connection between theories and models:
In the bolded sentence we learn about the connection between the models and the theories. Notice that there is not direct mention of the theory first discussed in the passage. Rather, at this point, the author is telling us the connection between models and theories. And basically we are told that in selecting a place to find minerals, people have to rely on conceptual models which are based on theories and other factors. So the theories form a base on which conceptual models can be built....and to maximize
the chances of discovery the explorer must therefore pay
particular attention to selecting the ground formations most
(30) likely to be mineralized. Such ground selection relies to
varying degrees on conceptual models, which take into
account theoretical studies of relevant factors.
These models are constructed primarily from empirical
observations of known mineral deposits and from theories
(35) of ore-forming processes.
Alright, let's turn to our answer choices:
Let's first look at (B). This answer choice is not the best because it distorts the relationship between conceptual models and theories. It tells us that the theories confirm the models. But we just read in the passage that theories form the basis for the models. So this distorts the relationship and is not a good choice. But looking at (A), we can see just what we are looking for based on what we read in the passage. We know that we are talking about the formation of minerals, like ore-so far so good. And then we get the clincher-"can support conceptual models." This is what we read at the end of the passage, so this is going to be your best choice.(A) It may furnish a valid account of ore-forming processes, and, hence, can support conceptual models that have great practical significance.
(B) It suggests that certain geological formations, long believed to be mineralized, are in fact mineralized, thus confirming current conceptual models.
I hope that I was able to help a little bit.
Happy studying!
